With the increase in the driving speeds of the automobiles and the increasing attention towards environmental protection, the innovation in the engine technology is developing in the direction of making engines having light weight, high efficiency, energy conservation and emission reduction. The gas distribution mechanism is an important part of an automobile engine. Since the rocker arm frame serves as a key part of the gas distribution mechanism, improvements in the structure of the rocker arm frame have important significance on the development of the engine.
As shown in FIG. 1, the rocker arm frame structure in the prior art is formed by stamping a metal plate. One end of the rocker arm frame is a ball socket, and the other end of the rocker arm frame is a curved crown part serving as a valve bearing surface. The structure of the curved crown part has a “W” shape, and the sidewall needs to be bent by 180 degrees during forming. The traditional forming process is that the plate material is firstly bent to form a “U” shape, which is then extruded and folded upwards to form a “W” shape. The defects of the existing structure are as below:
1. The local stretching and thinning phenomenon of the sidewall is serious, which influences the structural strength, resulting in the risk of fatigue fracture.
2. A gap exists between the two sidewalls which are not attached to each other, so the rigidity is poor and vibration noise can be generated during working, affecting normal operations of the engine.
3. More material is needed to fold the curved crown of the rocker arm frame, and thus the requirement for lightweight of the existing engine cannot be met.
4. The rocker arm frame forming process is complex and the cost is relatively high.